1. Field
Embodiments of the invention relate to the field of camera lens modules; and more specifically, to a camera module for use in portable digital devices.
2. Background
Many portable electronic devices, such as mobile cellular telephones, include a digital camera. The lenses for such cameras must be compact to fit within the case of the portable electronic device. At the same time there is a desire to provide an increasingly high quality camera function in these devices. To provide a higher quality image, some cameras found in portable electronic devices provide an autofocus feature.
The lens may be mounted in a mechanism that moves the lens along its optical axis to change the distance between the lens and the image sensor. This changes the focal distance of the camera and allows a sharper image to be obtained for subjects over a greater range of distances from the camera. One such lens moving mechanism for moving a lens is a voice coil motor (VCM).
Typically a lens is inserted into a lens moving mechanism, such as a VCM, and an image sensor is then assembled to the lens moving mechanism to provide a camera lens module. The module is assembled in clean room conditions so that dust is not trapped between the lens and the image sensor. The assembled camera lens module provides all the optical components in a single package that can be assembled into the portable electronic device.
Typically the lens will be joined to the lens moving mechanism by screw threads. The assembly is difficult because the lens and the lens moving mechanism are fairly delicate and the assembly must be done without exerting excessive forces on the lens or the mechanism, either axially or rotationally. The small size of the parts further complicates the assembly. A typical lens used in a portable electronic device may have a diameter of about 0.25 inches (6.5 millimeters).
A VCM for a camera module applications is a highly space constrained device. The demand for improved optics in camera module applications requires larger, heavier, lens components to be integrated within a VCM. A lens barrel is integrated within the VCM containing optical components of a lens system. Typically a cylindrical lens barrel is threaded in place within the carrier or holder of a VCM from the top opening furthest from the imaging plane. Typically the largest lens element within an optical system is the last element closest to the imaging plane.
It would be desirable to provide lens insertion methods and structures that allow the camera lens module to be reduced in size.